Wireless communication systems, such as the 3rd Generation (3G) of mobile telephone standards and technology, are well known. An example of such 3G standards and technology is the Universal Mobile Telecommunications System (UMTS™), developed by the 3rd Generation Partnership Project (3GPP™) (www.3gpp.org). The 3rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications. Such macro cells utilize high power base stations (NodeBs in 3GPP parlance) to communicate with wireless communication units within a relatively large geographical coverage area. Typically, wireless communication units, or User Equipment (UEs) as they are often referred to in 3G parlance, communicate with a Core Network (CN) of the 3G wireless communication system via a Radio Network Subsystem (RNS). A wireless communication system typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network. Each macro-cellular RNS further comprises a controller, in a form of a Radio Network Controller (RNC), operably coupled to the one or more Node Bs, via a so-called Tub interface.
The second generation wireless communication system (2G), also known as GSM, is a well-established cellular, wireless communications technology whereby “base transceiver stations” (equivalent to the Node B's of the 3G system) and “mobile stations” (user equipment) can transmit and receive voice and packet data. Several base transceiver stations are controlled by a Base Station Controller (BSC), equivalent to the RNC of 3G systems.
Communications systems and networks are developing towards a broadband and mobile system. The 3rd Generation Partnership Project has proposed a Long Term Evolution (LTE) solution, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN), for a mobile access network, and a System Architecture Evolution (SAE) solution, namely, an Evolved Packet Core (EPC), for a mobile core network. An evolved packet system (EPS) network provides only packet switching (PS) domain data access so voice services are provided by a 2G or 3G Radio Access Network (RAN) and circuit switched (CS) domain network. User Equipment (UE) can access a CS domain core network through a 2G/3GRAN such as the (Enhanced Data Rate for GSM Evolution, EDGE) Radio Access Network (GERAN) or a Universal Mobile Telecommunication System Terrestrial Radio Access Network (UTRAN), and access the EPC through the E-UTRAN. Some User Equipments have the capability to communicate with networks of differing radio access technologies. For example, a user equipment may be capable of operating within a UTRAN and within an E-UTRAN.
Lower power (and therefore smaller coverage area) cells are a recent development within the field of wireless cellular communication systems. Such small cells are effectively communication coverage areas supported by low power base stations. The terms “picocell” and “femtocell” are often used to mean a cell with a small coverage area, with the term femtocell being more commonly used with reference to residential small cells. Small cells are often deployed with minimum RF (radio frequency) planning and those operating in consumers' homes are often installed in an ad hoc fashion. The low power base stations which support small cells are referred to as Access Points (AP's) with the term Home Node B (HNB) or Evolved Home Node B (eHNB) defined by 3GPP to identify femtocell Access Points. Each small-cell is supported by a single Access Point. These small cells are intended to augment the wide area macro network and support communications to multiple User Equipment devices in a restricted, for example, indoor environment. Such small cells are intended to be able to be deployed “underneath” a macrocell (in a multi-layer structure, for example) in order to support communications to UEs in a restricted area such as a shopping mall, for example. An additional benefit of small cells is that they can offload traffic from the macro network, thereby freeing up valuable macro network resources). One or more Access Points are linked to a Core Network through an Access Controller. An Access Controller which links one or more HNB's to the Core Network is known as a Home Node B Gateway (HNB-GW). An HNB provides a radio access network connectivity to a user equipment (UE) using the so-called Iuh interface to a HNB-GW.
Typical applications for such Access Points include, by way of example, residential and commercial locations, communication ‘hotspots’, etc., whereby Access Points can be connected to a core network via, for example, the Internet using a broadband connection or the like. In this manner, small cells can be provided in a simple, scalable deployment in specific in-building locations where, for example, network congestion or poor coverage at the macro-cell level may be problematic.
Thus, an AP is a scalable, multi-channel, two-way communication device that may be provided within, say, residential and commercial (e.g. office) locations, ‘hotspots’ etc, to extend or improve upon network coverage within those locations. Although there are no standard criteria for the functional components of an AP, an example of a typical AP for use within a 3GPP 3G system may comprise Node-B functionality and some aspects of Radio Network Controller (RNC) functionality as specified in 3GPP TS 25.467. Herein, the term “small cell” means any cell having a small coverage area and includes “picocells” and “femtocells.”
Often in a small cell network, an Access Point Management System (AMS) is provided which may communicate with each Access Point and/or the Access Controller (HNB-GW). This management system is typically configured to manage a large number of Access Points, for example, monitoring, software upgrades, failure management and informing each Access Point of its assigned Location Area Code (or Routing Area Code). A Location Area Code (LAC) is a specific field in a Local Area Identifier which uniquely distinguishes one Location Area from others which are serviced by the same Mobile Switching Centre (MSC) of the Core Network. Some small cell systems employ a two-tiered LAC allocation scheme in order to maximize the number of supported small cells with distinct LAC's yet make the entire small cell system transparent to the core network (see for example US-A-20080207170).
When a User Equipment (UE) camps on to a particular HNB, for example, the HNB attempts to register the UE with the HNB-GW by sending a HNBAP UE register request message. The message can contain a UE identity and will be acknowledged with an accepted message if the registration is successful. The HNB broadcasts its assigned LAC which the UE detects and subsequently acknowledges that it is now operating in in that Location Area by sending a “Location Update” message. The HNB may monitor the UE via the periodic location updates. If a number of location updates are missed, the HNB assumes that the UE is no longer camped on and has left the HNB's' area of coverage. The HNB then informs the HNB-GW of this occurrence by sending a HNBAP deregister message.
A current industry model is to implement a GSMA one API on one of three places: viz. on the User Equipment (for handset applications) or on the small cell (for local applications) or on the application Gateway (for external third-party access). The GSMA one API is an application programming interface which has been developed by the GSM (Global System for Mobile Communications) Association. It is intended to be a web service interface. An application developed with one API can obtain information across network operators that support it. It is intended for operation on servers and mobile devices and the first API's to be implemented will be for messaging and location functions. Specifically, version 1 requires “location presence” capability and the ability to send and receive short message services (SMS) and multimedia messaging services (MMS) through the application Gateway using the GSMA one API.
“Presence” services in general permit an individual and equipment which he/she uses for communication to share information on the state of the individual and that equipment. Such information can include whether the individual and his communication equipment are currently able to communicate with others or are engaged on a video call, for example. “Presence” can also include information relating to the location of a user's communication equipment. A “presence server” may be provided in such instances for, on detection that a particular UE has entered a particular location, enabling applications that subscribe to a “presence” service to take some form of action. For example, location information can be very useful to retailers and advertisers who may wish to communicate with shoppers who are known to be in a certain location at a certain time, a shopping mall for example.
Some current Location Presence services are based on the use of a localised Identity Request sent by an Access Point to a UE to obtain its IMSI International Mobile Subscriber Identifier). This was originally proposed to support a form of access control. If the Access Point is prepared to offer normal telecommunications services, then the UE is allowed to register on the small cell. Alternatively, the IMSI may be captured from the so-called “Common_ID” sent by the Core network. In each case an Access Point must have a different LAC/RAC from the surrounding coverage (ie. other small cells or overlapping macrocell) in order to prompt a Registration attempt when camping on. A registration attempt may be used to prompt a location presence trigger. (See Applicant's co-pending Application GB 1209224.3).
In summary, current Location Presence services provide detection of a permitted user camping on an Access Point (or HNB). At this point a Registration will also be sent to the Core Network. This covers the scenarios of open access cells where all users are accepted for service; and the permitted user group of a closed access HNB.
In some circumstances (e.g. for traffic capacity reasons) it may be desirable for an AP to reject the UE so that it returns to the macro network. Two commonly-understood methods for achieving this are “LU (Location Update) Reject” (or, more generally, Registration Reject) or “Authentication Failure”. The latter method is not generally preferred as behavior varies across UEs and different 3GPP releases. A UE may also be rejected if it is not authorized to receive services from a particular Access Point ie. where there is Closed Access Control. Typically, the UE holds a “reject list” of LAC's from which it has been rejected. The capacity of this list is typically 10 LAC's. These stored LAC's are discarded on a cyclic first-in-first-out basis when the list reaches full capacity.
A further feature of the registration reject method is that a rejected UE is configured to delay trying to access an Access Point, having an LAC which is recorded in the reject list, for a lengthy period (typically 12-24 hours or the UE power-cycle). This is generally an advantage for Closed Access Control, but a disadvantage for a Location Presence service, as the UE will be prevented from re-accessing the same cell or from accessing another cell using the same LAC for a long period. Therefore, using known techniques, only UE's which are accepted on a cell and offered services can repeatedly re-register on a cell with the same LAC and so be detected again by a location presence service.